I got a reference circuit of AD8130 in application note AN-1214:
The note said that "The two 49.9 Ω resistors( in the red square) in series with the AD8130 input pins improve the overall distortion performance of the circuit". How these tow 49.9 Ω resistors improve the overall distortion performance of the circuit? After all, the differential input impedance of AD8130 is quite high(6 MΩ). If these tow resistors are close to the differential input port of AD8130, serious reflection will appear.